Annexins are a family of calcium- and phospholipid-binding proteins implicated in membrane fusion and ion channel formation. We have now obtained small crystals of annexin XII co-crystallized with phospholipid analogs. We propose to solve the structure of the annexin XII hexamer:phospholipid analog complex in the presence of calcium. 18 calcium sites on the perimeter of the disk shaped hexamer are accessible to the bulk solvent. The detailed atomic structure of this complex would provide new insight into the binding mode of the phospholipid headgroups to annexin XII.